The shading overall is done pretty well the only part that bugs me is the face the shading on it looks sort of flat. Maybe you could try having the light only illuminating under the chin and a few areas like this.. http://moo.thirddimension.net/evilchng.jpg
since the face is in front of the light source I think?

Oh you, he is very evil !!
hehe, well he was meant to look a bit cartoonish from the beginning, I'm not to good at drawing realistic stuff...I'm better at cartoons...but im learning
And I totally agree on the shading of the face, I was very unsure about that, I tried shading it like mOO suggested, but it just didn't look good..so I just kept it, as it was...but ill look into your suggestions!
and he is evil!
*mental note: need to learn how to draw good textures*